Direct evidence of soft mode behavior near the Burns temperature in the PbMg 1 / 3 Nb 2 / 3 </mml:…
2002; American Physical Society; Volume: 66; Issue: 21 Linguagem: Inglês
10.1103/physrevb.66.214101
ISSN1095-3795
AutoresS. B. Vakhrushev, Stuart Shapiro,
Tópico(s)Photorefractive and Nonlinear Optics
ResumoInelastic neutron scattering measurements of the relaxor ferroelectric ${\mathrm{PbMg}}_{1/3}{\mathrm{Nb}}_{2/3}{\mathrm{O}}_{3}$ (PMN) in the temperature range $490\mathrm{K}<T<880\mathrm{K}$ directly observe the soft mode (SM) associated with the Curie-Weiss behavior of the dielectric constant $\ensuremath{\varepsilon}(T).$ The results are treated within the framework of the coupled SM and transverse optic (TO1) mode and the temperature dependence of the SM frequency at ${q=0.075a}^{*}$ is determined. The parameters of the SM are consistent with the earlier estimates and the frequency exhibits a minimum near the Burns temperature $(\ensuremath{\approx}650\mathrm{K}).$
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